This invention relates generally to the field of detecting devices, and more particularly to devices capable of detecting objects, for example, in a vehicle operator""s blind spot.
Motor vehicle drivers are required to negotiate traffic safely when travelling on public roads. For this reason, cars, trucks and other road-travelling motor vehicles are typically equipped with mirrors positioned both inside and outside the vehicle. The mirrors allow the driver to see a portion of the road behind or beside the vehicle with only a slight shift of the eyes or turn of the head. If other vehicles are visible the driver will be suitably alerted and in position to avoid making an inappropriate move, such as a lane change.
Having an awareness of the presence of neighbouring vehicles is particularly important when changing lanes, either to the left or the right. To change lanes safely the driver needs to ascertain beforehand that there is no vehicle in the adjacent lane. However, for simple reasons of geometry the mirrors that are commonly factory installed in motor vehicles only provide a partial view of the space immediately to the side and towards the back of the vehicle, which needs to be clear to change lanes. The unviewable space, commonly called the xe2x80x9cblind spotxe2x80x9d, is therefore typically checked by the driver physically turning his or her head to the side in a so called xe2x80x9cshoulder checkxe2x80x9d so that the space can be viewed directly. When it is confirmed that the space is clear and that there is no other vehicle fast approaching, the driver can move their vehicle into the desired lane.
While turning one""s head can be a partially effective way to check the blind spot, it also creates a safety risk since it forces the driver to take his or her eyes away from the road directly in front of the vehicle. In particular, there is a risk of a collision with a vehicle in the space ahead if that vehicle brakes or decelerates quickly in the moment that the driver is checking the blind spot. Even if the driver does notice the vehicle in front when his eyes return, it may be too late to stop safely. This risk becomes even more acute when driving conditions are less than optimal, such as in heavy traffic, or when there is poor visibility due to night time darkness or adverse weather conditions such as snow or ice on the road. Further, there will always be drivers with limited or no head mobility due to disability or a stiff neck, as well as people with slower than average reaction times such as seniors. Also, drivers of large vehicles such as trucks that sit high above the road may have difficulty seeing small vehicles occupying the lane on the passenger side. Drivers operating under such conditions are much more susceptible to the risk of an accident when changing lanes. Lastly, even with a shoulder check, portions of the field of view will be unviewable due to door pillars, condensation, snow, and the like. It is desired to reduce the number of checks made of the blind spot to reduce the risk of a dangerous situation arising without changing normal safe driving practices or requirements.
For these reasons various attempts have been made in the past to create a safety device capable of automatically detecting the presence of a target vehicle in the blind spot. If possible, this would reduce the need for a xe2x80x9cshoulder checkxe2x80x9d when a lane change can""t occur because the desired lane is occupied by another vehicle, without changing normal safe driving practices or requirements. Ideally the device informs the driver whether the lane is clear or occupied, so that the driver need only shoulder check to confirm the lane is clear to change lanes safely while keeping most of his or her attention on the road ahead.
One known type of detecting device taught in U.S. Pat. No. 5,112,796 to Beggs et al actively emits a signal, for example in a short wavelength infrared region, and then detects the presence or absence of a reflected wave from a target vehicle. Active devices such as this however are relatively complex and need both a transmitter and a receiver. Because of the complexity of the components and the number of elements required, such as electrical connection, power supply, signal emitter, and signal detector, active systems tend to be expensive. Further, failure of any one component means the whole system fails. As well, such systems tend to create false positive alarms, due to reflection of the signal off of stationary objects such as parked cars and the like. As a result, such systems have not been broadly commercially deployed.
Another approach involves the use of a thermal emitted radiation detector of the type found in security system motion detectors. These detectors can be used to passively sense the heat being generated as a matter of course by any target vehicle. Such a detector needs no emitter and therefore has the advantage of a relatively simple and inexpensive design. However, this type of detector requires a change in temperature to create a detectable event and therefore is generally only effective when the target vehicle enters or leaves the field of view of the detector. Target vehicles that are travelling at the same speed as the host vehicle or sensor platform and that remain in a fixed position in the blind spot may become undetectable. Thus, a driver may mistakenly assume a vehicle has passed through the blind spot when in fact it remains there. A lane change in such a case could result in an accident.
This particular issue is addressed in the device described in U.S. Pat. No. 5,668,539 to Patchell, the present inventor. In this device thermal emission readings are obtained from a reference position on the road immediately beside the host vehicle, where it is expected that there will be no other vehicle, as well as from at least one position in the blind spot itself. The reference and other emission readings are compared and a detection event arises if there is a substantive difference between the two values. This device however produces false alarms when there is a variation in road temperature between the reference spot and blind spot, such as the cool area created by a shadow under a bridge on a sunny day. Thus, this prior device also suffers from a statistically small but unacceptably high level of false detection events.
What is needed is a detection system which is simple, inexpensive, and reliable, and which does not produce an unacceptable level of false detection events. In the absence of any solution that addresses the practical problems of detecting a target vehicle in a blind spot under real road, traffic, and weather conditions, tragic and costly accidents due to driver blind spot miscalculation will continue to occur.
What is required is a detecting device and method which overcomes the problems associated with the current devices and methods used for detecting objects such as target vehicles in a blind spot.
Most particularly, the device and method should reliably and accurately alert a driver when a target vehicle has either entered, or is within or exits a blind spot. The device should be able to provide alerts for blind spots on either one or on both sides of the vehicle, as desired. The device and method should just as reliably and accurately avoid false alarms, that is, alerts indicating that there is a vehicle in the blind spot when in fact the lane is clear. Further, it is desirable that the device and method""s capacity to render accurate alerts and avoid false alarms remain effective for all practical variations in road, traffic, and weather conditions. This may include, for example, light and dark asphalt, smooth, bumpy, or pot-holed roads, light or heavy traffic, and the presence of sunlight, rain, snow, or ice on the road. As well, the device and method should operate effectively in the presence of shadows cast by nearby or overhead structures such as bridges and naturally occurring objects like trees.
It would be further advantageous for the device to be sufficiently versatile to be used with passenger cars as well as larger vehicles such as recreational vehicles and trucks. Yet another desirable feature would be for the device to be able to measure the absolute temperature of the road, so that warnings of potential black ice conditions could be provided to the driver.
According to the present invention, such a device and method are preferably achieved by successively sampling the level of electromagnetic radiation in a predetermined frequency range from a given position in space in the blind spot, and by comparing the (time adjusted) samples. In this way, common factors that influence the level of such electromagnetic radiation will tend to cancel out. At the same time, the appearance of a passing object such as a vehicle in the blind spot will produce a substantive signal value since successive samples of a given position in space will register different values of electromagnetic radiation as the vehicle passes through the monitored position. This signal value can be then used to trigger an alert for the driver.
According to a first aspect of the present invention, there is provided a detecting device for detecting moving target vehicles from a moving host vehicle, said device comprising:
a first detector means mounted to said host vehicle and aligned to a stationary target area for generating at least a first output representative of said stationary target area at least at a time T1;
a second detector means mounted to said host vehicle and aligned to said stationary target area for generating at least a second output representative of said stationary target area at least at a time T2; and
a control system to receive said first and second outputs, and to compare said first output at time T1 to said second output at time T2 to identify any differences between said outputs;
whereby a target vehicle moving in said stationary target area may be detected.
According to a second aspect of the present invention there is provided a method for detecting moving target vehicles from a moving host vehicle, said method comprising:
providing a first detector means mounted to said host vehicle and aligned to a stationary target area for generating at least a first output representative of said stationary target area at a time T1, a second detector means mounted to said host vehicle and aligned to said stationary target area for generating at least a second output representative of said stationary target area at a time T2, and a control system to receive said first and second outputs and to compare said first output at T1 to said second output at T2 to identify any differences between said outputs;
generating said first output at time T1, and receiving said first output into said control system;
generating said second output at time T2, and receiving said second output into said control system;
comparing said first and second outputs; and
providing an indication of a target vehicle moving in said stationary target area if said comparison of said first and second outputs identifies any differences between said outputs.